U.S. patent application number 15/252207 was filed with the patent office on 2017-03-02 for fixing device using stainless steel material.
This patent application is currently assigned to K.K. ENDO SEISAKUSHO. The applicant listed for this patent is K.K. ENDO SEISAKUSHO. Invention is credited to Katsutoshi Maruyama, Hiroyuki Toyama, Takashi Yaoita.
Application Number | 20170060058 15/252207 |
Document ID | / |
Family ID | 56920490 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170060058 |
Kind Code |
A1 |
Toyama; Hiroyuki ; et
al. |
March 2, 2017 |
FIXING DEVICE USING STAINLESS STEEL MATERIAL
Abstract
A thin aluminum surface layer is formed on the outer peripheral
surface of a tubular body of stainless steel material as a base
layer to provide a fixing member. For forming the thin aluminum
surface layer, arc thermal spraying apparatus is used such that
material of a wire rod for thermal spraying is aluminum with purity
of 99%, diameter of the wire rod is .phi. 1.2 mm, distance of
thermal spraying is 120 mm, shifting velocity of the spraying gun
is 20 mm/sec and air pressure is 0.5 MPa. Rotating the tubular body
of stainless steel as a base layer at 150 rpm, thermal spraying of
aluminum is performed with the spraying gun being shifted in the
direction parallel to the axial direction of the tubular body of
stainless steel as shown by the arrow. The thickness of the
thermally sprayed aluminum surface layer is 20 to 30 .mu.m.
Inventors: |
Toyama; Hiroyuki; (Niigata,
JP) ; Maruyama; Katsutoshi; (Niigata, JP) ;
Yaoita; Takashi; (Niigata, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
K.K. ENDO SEISAKUSHO |
Niigata-ken |
|
JP |
|
|
Assignee: |
K.K. ENDO SEISAKUSHO
Niigata-ken
JP
|
Family ID: |
56920490 |
Appl. No.: |
15/252207 |
Filed: |
August 30, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 4/123 20160101;
G03G 15/2057 20130101 |
International
Class: |
B23P 6/00 20060101
B23P006/00; G03G 15/20 20060101 G03G015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2015 |
JP |
2015-170453 |
Claims
1. A fixing device using a stainless steel material for heating
toner to fix toner images on recording media in an image forming
apparatus in which copying is performed through toner; the fixing
device being equipped with a thin tubular fixing member heated by a
heating element disposed therein, and the thin tubular fixing
member being formed through: a step of forming a cup-shaped tubular
body of stainless steel material having a thickness of 20 .mu.m to
300 .mu.m by fitting a mandrel into an inner peripheral surface of
the cup-shaped tubular body of stainless steel material and
performing spinning with a roller/rollers pressed and shifted in
the axial direction during rotation of the cup-shaped tubular body
to elongate the cup-shaped tubular body in the axial direction, a
step of cutting off both ends of the cup-shaped tubular body to
form a tubular body of stainless steel material as a base layer, a
step of aluminum thermal spraying on an outer peripheral surface of
the tubular body of stainless steel material to form an aluminum
surface layer having a thickness of 10 .mu.m to 150 .mu.m thereon,
and a step of forming a releasing layer on the aluminum surface
layer.
2. The fixing device using a stainless steel material according to
claim 1, wherein the base layer of the fixing member is either the
base layer with a thickness of 20 .mu.m to 50 .mu.m of a fixing
sleeve or the base layer with a thickness of 100 .mu.m to 300 .mu.m
of a fixing roller, and the thickness of the aluminum surface layer
is 15% to 50% of the base layer.
3. The fixing device using a stainless steel material according to
claim 2, wherein the heating element is a halogen heater.
4. The fixing device using a stainless steel material according to
claim 3, wherein the steps for forming the thin tubular fixing
member further comprise a step of performing sandblasting of the
outer peripheral surface of the tubular body of stainless steel
material to roughen the outer peripheral surface as a step before
the step of aluminum thermal spraying on the outer peripheral
surface of the tubular body of stainless steel material.
5. The fixing device using a stainless steel material according to
claim 4, wherein a maximum height roughness Rmax of the outer
peripheral surface of the aluminum surface layer is no more than 40
.mu.m.
6. The fixing device using a stainless steel material according to
claim 5, wherein the steps for forming the thin tubular fixing
member further comprise a step of polishing the outer peripheral
surface of the tubular body of stainless steel material to remove
convex portions thereof as a step after the step of aluminum
thermal spraying on the outer peripheral surface of the tubular
body of stainless steel material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of Japanese
application serial no. 2015-170453, filed on Aug. 31, 2015. The
entirety of the above-mentioned patent application is hereby
incorporated by reference herein and made a part of this
specification.
FIELD OF THE INVENTION
[0002] The present invention relates to a fixing device provided
with a fixing member having a thin tubular shape using a stainless
steel material and particularly relates to a fixing device provided
with a fixing sleeve or fixing roller for fixing toner on a paper
sheet by applying heat and pressure in a laser printer or copying
machine.
BACKGROUND OF THE INVENTION
[0003] The fixing method of a laser printer or copying machine is
being changed from a conventional fixing method with a roller to
one with a film. With the conventional fixing method with a roller,
it is necessary to keep the heater operated even in time of waiting
so as to heat the roller with the heater inside of the roller. In
contrast to this, a fixing sleeve formed to have a small thickness
enables power saving and shortening of waiting time since it has a
high thermal conductivity and a small heat capacity and the heater
is operated only when the fixing tube is rotated. While metal
materials such as stainless steel or resin materials such as
polyimide are used for the thin tube as the base layer of this
fixing sleeve, metal materials such as stainless steel having high
strength and small heat capacity are preferable in order to secure
power saving or shortening of waiting time.
[0004] Flexibility in the circumferential direction bearable to
deformation and durability are required for a fixing sleeve. In the
case where a stainless steel material is used for a base layer, the
base layer is formed so as to be extremely thin as a thickness of
20 .mu.m to 50 .mu.m. As a method for forming a such an extremely
thin metal tube, it is known to use spinning (see Patent Document
1).
[0005] An extremely thin fixing sleeve using a stainless steel
material is excellent in thermal responsiveness since it has a
small heat capacity as the specific heat is small compared with a
conventional fixing sleeve made of an aluminum material). Further,
an extremely thin fixing sleeve using a stainless steel material
has a thin thickness, so that temperature rising becomes fast in
the direction of thickness. However, a fixing sleeve using a
stainless steel material is inferior in thermal conductivity in its
axial direction since thermal conductivity of the stainless steel
sleeve is low compared with a conventional fixing sleeve made of an
aluminum material. Furthermore, while a fixing sleeve is deprived
of heat in the central portion in the axial direction, when paper
is fed through, temperature is raised in the end portions in the
axial direction. Accordingly, temperature is not even in the axial
direction, thus giving a problem of so called thermal unevenness in
a fixing sleeve.
[0006] There is a method of applying copper plating having a high
thermal conductivity on the outer peripheral surface of a tubular
body as a base layer made of a stainless steel material for solving
thermal unevenness in a fixing sleeve. However, this method
provides a problem such that it is not likely for the paint such as
rubber to be securely attached to the peripheral surface of the
sleeve plated with copper due to influence of oxidized copper
surface layer.
[0007] There is another method of forming an extremely thin metal
tubular body by spinning of a laminated material (a clad material)
of stainless steel with copper or of stainless steel with aluminum
for solving thermal unevenness in a fixing sleeve. However, this
method provides a problem such that expense for manufacturing
becomes higher since price of such a laminated material is
high.
[0008] There is still another method of performing thermal spraying
of aluminum having a high thermal conductivity on the outer
peripheral surface of a tubular body as a base layer for solving
thermal unevenness in a fixing sleeve (Patent Documents 1 to 4).
Further, a halogen heater utilizing radiant heat radiated from a
halogen lamp enables heating just after turning on of the power
source switch and has stability, with low expense required.
However, it is difficult to employ a halogen lamp for a thick
fixing sleeve, since it has a large heat capacity to require time
for raising the temperature of the fixing sleeve.
[0009] Regarding the fixing member disclosed in Patent Document 1,
there is no disclosure of the thickness of the stainless steel
material forming the base layer. Here, the thickness of the
aluminum surface layer thermally sprayed thereon is more than 5
.mu.m and the heating element disposed inside of the stainless
steel tubular body is liquid heating medium 13 or a heater 15.
[0010] Regarding the fixing member disclosed in Patent Document 2,
there is no disclosure of the thickness of the stainless steel
material forming the base layer and the thickness of the aluminum
surface layer thermally sprayed thereon. Further, there is no
disclosure of the heating element disposed inside of the stainless
steel tubular body. Regarding the fixing member disclosed in Patent
Document 3, there is no disclosure of the thickness of the
stainless steel material forming the base layer. Further, the
thickness of the aluminum surface layer thermally sprayed thereon
is 1.5 mm, thus not being a thin aluminum surface layer.
Furthermore, the heating element disposed inside of the stainless
steel tubular body is a coil 5 for electromagnetic induction.
[0011] While in the fixing member discloses in Patent Document 4,
the thickness of the stainless steel material as a base layer is 30
.mu.m to 200 .mu.m, it is not disclosed that aluminum is thermally
sprayed on the outer peripheral surface of the stainless steel as a
base layer. Furthermore, the heating element disposed inside of the
stainless steel tubular body is a ceramic heater 11.
PRIOR ART DOCUMENT
Patent Document
[0012] Patent Document 1: JP Publication of Patent Application No.
S53-120537 Patent Document 2: JP Publication of Patent Application
No. H08-95410
Patent Document 3: JP Publication of Patent Application No.
2001-109307
Patent Document 4: JP Publication of Patent Application No.
2003-156954
SUMMARY OF THE INVENTION
[0013] The present invention provides a fixing device, in which
temperature rising speed in the thickness direction is high,
temperature distribution is uniform in the axial direction with
little thermal unevenness on the fixing member and less energy is
required for heating the fixing member, by forming a thin aluminum
surface layer on the outer peripheral surface of a thin stainless
steel tubular body as a base layer.
[0014] The fixing device using a stainless steel material according
to the first aspect of the present invention is one using a
stainless steel material for heating toner to fix toner images on
recording media in an image forming apparatus in which copying is
performed through toner;
[0015] the fixing device being equipped with a thin tubular fixing
member heated by a heating element disposed therein, and
[0016] the thin tubular fixing member being formed through: [0017]
a step of forming a cup-shaped tubular body of stainless steel
material having a thickness of 20 .mu.m to 300 .mu.m by fitting a
mandrel into an inner peripheral surface of the cup-shaped tubular
body of stainless steel material and performing spinning with a
roller/rollers pressed and shifted in the axial direction during
rotation of the cup-shaped tubular body to elongate the cup-shaped
tubular body in the axial direction, [0018] a step of cutting off
both ends of the cup-shaped tubular body to form a tubular body of
stainless steel material as a base layer, a step of aluminum
thermal spraying on an outer peripheral surface of the tubular body
of stainless steel material to form an aluminum surface layer
having a thickness of 10 .mu.m to 150 .mu.m thereon, and [0019] a
step of forming a releasing layer on the aluminum surface
layer.
[0020] The fixing device using a stainless steel material according
to the second aspect of the present invention is characterized in
that, in the first aspect, the base layer of the fixing member is
either the base layer with a thickness of 20 .mu.m to 50 .mu.m of a
fixing sleeve or the base layer with a thickness of 100 .mu.m to
300 .mu.m of a fixing roller, and the thickness of the aluminum
surface layer is 15% to 50% of the base layer.
[0021] The fixing device using a stainless steel material according
to the third aspect of the present invention is characterized in
that, in the second aspect, the heating element is a halogen
heater.
[0022] The fixing device using a stainless steel material according
to the fourth aspect of the present invention is characterized in
that, in the third aspect, the steps for forming the thin tubular
fixing member further comprise a step of performing sandblasting of
the outer peripheral surface of the tubular body of stainless steel
material to roughen the outer peripheral surface as a step before
the step of aluminum thermal spraying on the outer peripheral
surface of the tubular body of stainless steel material.
[0023] The fixing device using a stainless steel material according
to the fifth aspect of the present invention is characterized in
that, in the fourth aspect, a maximum height roughness Rmax of the
outer peripheral surface of the aluminum surface layer is no more
than 40 .mu.m.
[0024] The fixing device using a stainless steel material according
to the sixth aspect of the present invention is characterized in
that, in the fifth aspect, the steps for forming the thin tubular
fixing member further comprise a step of polishing the outer
peripheral surface of the tubular body of stainless steel material
to remove convex portions thereof as a step after the step of
aluminum thermal spraying on the outer peripheral surface of the
tubular body of stainless steel material.
[0025] In the fixing device according to the present invention
using a stainless steel material, a thin aluminum surface layer is
formed on the outer peripheral surface of a tubular body made of a
thin stainless steel material as a base layer, so that temperature
rising speed in the thickness direction is high, temperature
distribution is uniform in the axial direction with little thermal
unevenness on the fixing member and less energy is required for
heating the fixing member. Further, a halogen heater can be used as
a heating element, heating of the fixing member can be made just
after turning on of the power switch and stability of the device is
improved along with less expense required, since the fixing member
has a small heat capacity.
BRIEF EXPLANATION OF DRAWINGS
[0026] FIG. 1 is an explanatory view showing a schematic
composition of an image forming apparatus to which the fixing
device according to the present invention is applied.
[0027] FIG. 2 is an explanatory sectional view showing the fixing
device using a stainless steel material according to the present
invention.
[0028] FIG. 3 is a flowchart showing the method for manufacturing
the fixing member using a stainless steel material according to the
present invention.
[0029] FIGS. 4(a) and 4(b) are views showing the method for
manufacturing the fixing roller according to an embodiment of the
present invention, in which FIG. 4(a) is a longitudinal sectional
view showing a forming step of a cup-shaped tubular body by deep
drawing and FIG. 4(b) is a perspective view showing the formed
cup-shaped tubular body.
[0030] FIGS. 5(a) and 5(b) are views showing steps after FIGS. 4(a)
and 4(b), in which FIG. 5(a) is an explanatory view showing a step
of spinning the cup-shaped tubular body shown in FIG. 4(b) using a
mandrel and FIG. 5(b) is a view showing a step of forming a tubular
fixing roller by cutting off the cup-shaped tubular body after the
spinning step at both ends thereof.
[0031] FIG. 6 is an explanatory view showing a step of sandblasting
to the tubular fixing roller in which both ends have been cut
off.
[0032] FIG. 7 is a view showing, as a step after FIG. 6, a step of
thermally spraying aluminum on the tubular fixing roller in which
both ends have been cut off.
[0033] FIGS. 8(a) and 8(b) are photographs showing the outer
peripheral surface of the fixing roller on which aluminum is
thermally sprayed, in which FIG. 8(a) is a photograph showing the
whole outer peripheral surface of the fixing roller and FIG. 8(b)
is an enlarged photograph showing the area surrounded by the
rectangular frame line in FIG. 8(a).
[0034] FIG. 9 is microscopic photographs in magnification of five
kinds showing three sites in FIGS. 8(a) and 8(b).
[0035] FIGS. 10(a), 10(b) and 10(c) are graphs showing the surface
roughness measured at three sites on the fixing roller on which
aluminum has been thermally sprayed, respectively.
[0036] FIG. 11 is a table showing data of the surface roughness
shown in FIGS. 10(a), 10(b) and 10(c).
[0037] FIGS. 12(a), 12(b) and 12(c) are graphs showing the surface
roughness measured at three sites on the fixing roller after
polishing has been performed on the outer peripheral surface of the
aluminum surface layer, respectively.
[0038] FIG. 13 is a table showing data of the surface roughness in
FIGS. 12(a), 12(b) and 12(c).
[0039] FIG. 14 is an explanatory sectional view showing the fixing
roller in a state where a releasing layer of fluorocarbon polymers
has been formed on the outer peripheral surface of the aluminum
surface layer.
DETAILED EXPLANATION OF EMBODIMENTS
[0040] (General Explanation of an Image Forming Apparatus)
[0041] Embodiments of the present invention will be explained
referring to drawings below.
[0042] FIG. 1 is an explanatory view showing a schematic
composition of an image forming apparatus to which the fixing
device according to the present invention is applied. While the
present invention relates to a fixing device 9, the composition of
an image forming apparatus 1, to which the fixing device 9 is
applied, is generally explained first. Various arrangements are
known for the image forming apparatus 1. Here, exemplifying it for
a laser printer as an image forming apparatus, the image forming
apparatus 1 is composed of a main body 2, an exposure device 3, a
photosensitive element 4, a transfer portion 5, a paper tray 6, a
paper feeding portion 7, resist rollers 8, a fixing device 9, etc.
Since the function and composition of each portion are known,
detailed explanation is omitted here.
[0043] Next, operation of the image forming apparatus 1 will be
explained generally. At the time of copying, laser beam light A
carrying an image to be formed is irradiated in the exposure device
3 onto the photosensitive element 4. Steps of charge, exposure and
development proceed as the drum mounting the photosensitive element
4 thereon is rotated, then toner image is formed with toner 11 on
the photosensitive element 4. The toner 11 takes a form of
particles, each of which contains coloring material and wax within
it, and an image with such toner is formed on the photosensitive
element 4 through the steps mentioned above. This image of toner is
transferred, in the transfer portion 5 via transferring rollers
provided to meet the photosensitive element 4, onto the paper 12
fed from the paper feeding portion 7 through the resist rollers
8.
[0044] The paper 12 having passed the transfer portion 5 is sent to
the fixing device 9. The paper 12 is fed as sandwiched between a
fixing roller 13 and a pressure roller 14 and a toner image is
fixed on the paper 12 with heat and pressure. The paper 12 with
fixing performed is sent as shown by an arrow to be ejected as a
printed image to the paper tray 6. Copying with a laser printer is
performed basically through the above mentioned steps.
[0045] In the next, a fixing device 9 will be explained. FIG. 2 is
an explanatory sectional view showing the fixing device using a
stainless steel material according to the present invention. The
fixing device 9 according to the present invention is basically
composed of a fixing roller 13, a pressure roller 14, a halogen
heater as a heating element 15, etc. This device is arranged so
that the toner image on the paper 12 is fixed with the pressure
roller 14 pressed to the thin tubular fixing roller 13. Explaining
the fixing roller first, the fixing roller 13 is heated with the
halogen heater as the heating element 15 disposed inside of the
fixing roller 13.
[0046] The fixing roller (fixing member) 13 is formed of a
stainless steel material as a base layer having a thickness of 100
.mu.m to 300 .mu.m. In place of the rather thick fixing roller 13,
a fixing sleeve (a fixing film as a fixing member) formed of an
extremely thin stainless steel material having a thickness of 20
.mu.m to 50 .mu.m may be employed. With such an extremely thin
fixing sleeve, fixing with heating in quick start is possible by
forming a nipped portion having a predetermined width between the
pressure roller 14 and the heating element 15 and pressing the
fixing sleeve with only the nipped portion heated.
[0047] (Manufacturing Method of the Fixing Roller)
[0048] FIG. 3 is a flowchart showing the method for manufacturing
the fixing member using a stainless steel material according to the
present invention. FIGS. 4(a) and 4(b) shows the method for
manufacturing the fixing roller according to an embodiment of the
present invention, in which 4(a) is a lengthwise sectional view
showing a forming step of a cup-shaped tubular body by deep drawing
as STEP 1 in FIGS. 3 and 4(b) is a perspective view showing the
formed cup-shaped tubular body 200. A fixing sleeve formed of an
extremely thin stainless steel material with a thickness of 20
.mu.m to 50 .mu.m can be also manufactured in a similar method as a
fixing roller. As shown in FIG. 4(a), a thin sheet 100 of stainless
steel SUS304, etc., is worked by deep drawing with a female die 101
and a punch 102 to form a cup-shaped tubular body 200 as shown in
FIG. 4(b).
[0049] FIGS. 5(a) and 5(b) shows a step after one shown in FIGS.
4(a) and 4(b). Here, FIG. 5(a) is an explanatory view showing a
step of spinning as STEP 2 in FIG. 3, that is, a step of spinning
the cup-shaped tubular body 200 with a mandrel, and FIG. 5(b) is an
explanatory view showing STEP 3 in FIG. 3, that is, a step of
forming a tubular fixing roller by cutting off the cup-shaped
tubular body 200 after the spinning step at both ends thereof. More
particularly, the mandrel 300 of a spinning machine is fitted into
the inner peripheral surface 201 of the cup-shaped tubular body 200
and the mandrel 300 is rotated to rotate the cup-shaped tubular
body 200, as shown in FIGS. 5(a) and 5(b).
[0050] Working by spinning is performed by pressing rollers 301,
301 onto the outer peripheral surface 202 of the cup-shaped tubular
body 200 and causing the rollers 301, 301 to move in the axial
direction of the cup-shaped tubular body 200. With this, the
cup-shaped tubular body 200 is subjected to plastic deformation in
its axial direction to be thin and elongated in its axial
direction. As shown in FIG. 5(b), cutting off the cup-shaped
tubular body 200 having spinning finished at its both ends with
cutting-off tools 302, 302, a tubular body 400 of a stainless steel
material having a thickness of 100 .mu.m to 300 .mu.m as a base
layer of the fixing roller 13 is obtained. It is also possible to
form a tubular body 400 of a stainless steel material having a
thickness of 20 .mu.m to 50 .mu.m that can be used as a fixing
sleeve in a similar working by spinning.
[0051] FIG. 6 shows a step after one shown in FIG. 5 as an
explanatory view showing STEP 4 in FIG. 3, that is, a step of
sandblasting to the tubular body 400 of a stainless steel material
as a base layer. As shown in FIG. 6, the tubular body 400 of a
stainless steel material as a base layer according to the
embodiment of the present invention has such dimension as an outer
diameter D of .phi. 20 mm, an axial length L1 of 258 mm and a
thickness t1 of 100 .mu.m. A sandblasting machine of a suction type
is used for sandblasting such that grinding material 501 is of
alumina #60, distance L2 of blasting is 200 mm, time of blasting is
30 seconds and air pressure is 0.4 MPa. Rotating the tubular body
400 of a stainless steel material as a base layer at 150 rpm,
sandblasting was performed with the sandblasting nozzle 500 of the
sandblasting machine being shifted in the direction parallel to the
axial direction of the tubular body 400 (as shown by the arrow
502).
[0052] FIG. 7 shows a step after one shown in FIG. 6 as an
explanatory view showing STEP 5 in FIG. 3, that is, a step of
thermal spraying of aluminum on the outer peripheral surface of the
tubular body 400 of a stainless steel material as a base layer. As
shown in FIG. 7, an arc thermal spraying apparatus is used for
thermal spraying such that material of a wire rod for thermal
spraying is aluminum with purity of 99%, diameter of the wire rod
is .phi. 1.2 mm, distance L3 of thermal spraying is 120 mm,
shifting velocity of the spraying gun 601 is 20 mm/sec and air
pressure is 0.5 MPa. Rotating the tubular body 400 of a stainless
steel material as a base layer at 150 rpm, thermal spraying of
aluminum was performed with the spraying gun 601 of the arc thermal
spraying apparatus being shifted in the direction parallel to the
axial direction of the tubular body 400 of a stainless steel
material (as shown by the arrow 602). The thickness t2 of the
thermally sprayed aluminum surface layer 401 is 20 .mu.m to 30
.mu.m. The aluminum to be thermally sprayed may be an aluminum
alloy.
[0053] It is possible to form a reversed crown shaped aluminum
surface layer 401 by varying the thickness t2 of the thermally
sprayed aluminum surface layer 401 in the axial direction during
thermal spraying. That is, by controlling the shifting velocity of
the spraying gun 601 corresponding to the position in the axial
direction on the tubular body 400 of a stainless steel material as
a base layer (with the shifting velocity being gradually slower in
the position near the both ends than in the position near the
center portion in the axial direction), the aluminum surface layer
401 of the tubular body 400 of a stainless steel material as a base
layer is formed so as to be thin in the central portion in the
axial direction and to become gradually thicker towards the both
ends in the axial direction. As a result, the central portion has a
small heat capacity due to being thinner and the portions near to
the both ends have a large heat capacity due to being thicker.
Consequently, although the temperature in the central portion in
the axial direction of the fixing roller 13 is lowered than in the
portions at both ends through feeding paper, the temperature in the
central portion in the axial direction of the fixing roller 13 can
be raised in a short time since heat capacity of the portion is
small. By virtue of this, thermal unevenness on the fixing roller
13 can be made less.
[0054] FIGS. 8(a) and 8(b) are photographs showing the outer
peripheral surface of the fixing roller 13 on which aluminum is
thermally sprayed, in which 8(a) is a photograph showing the whole
outer peripheral surface of the fixing roller 13 and 8(b) is a
photograph enlarged in a magnification of 12 times and showing the
area surrounded by the rectangular frame line in 8(a). FIG. 9 is
microscopic photographs in magnification of five kinds showing
three sites in FIGS. 8(a) and 8(b). FIGS. 10(a), 10(b) and 10(c)
are graphs showing the surface roughness measured at three sites,
that is, at Flange, Bottom and Center on the fixing roller on which
aluminum is thermally sprayed, respectively. FIG. 11 is a table
showing data of the surface roughness shown in FIGS. 10(a), 10(b)
and 10(c). As seen from the state of the formed cup-shaped tubular
body 200 as shown in FIG. 5(a), FIG. 5(b), the open end side is
called as Flange, the bottom side is called as Bottom and the
intermediate portion between the open end side and the bottom side
is called as Center. As seen in FIGS. 10(a), 10(b) and 10(c) and
11, the outer peripheral surface of the fixing roller 13 on which
aluminum has been thermally sprayed has a surface roughness such
that Ra (Center line average roughness) is 7.366 .mu.m to 9.929
.mu.m, Rz (Ten point average roughness) is 27.770 .mu.m to 35.516
.mu.m and Rmax (Maximum height roughness) is 56.388 .mu.m to 73.038
.mu.m.
[0055] In the next, the outer peripheral surface of the fixing
roller 13 on which aluminum has been thermally sprayed is polished
in STEP 6 shown in FIG. 3. Rotating the fixing roller 13 along with
shifting a polishing tool in the direction parallel to the axial
direction of the fixing roller 13, the convex portions on the outer
peripheral surface of the fixing roller are removed away to smooth
the outer peripheral surface of the aluminum surface layer. FIGS.
12(a), 12(b) and 12(c) are graphs showing the surface roughness
measured at three sites, that is, at Flange, Bottom and Center, on
the outer peripheral surface of the aluminum surface layer 401
after polishing has been performed, respectively, and FIG. 13 is a
table showing the data of the surface roughness in FIGS. 12(a),
12(b) and 12(c). As shown in FIGS. 12(a), 12(b) and 12(c) and 13,
the outer peripheral surface of the fixing roller 13 having been
subjected to polishing has a surface roughness such that Ra (Center
line average roughness) is 6.892 .mu.m to 7.330 .mu.m. Rz (Ten
point average roughness) is 23.949 .mu.m to 25.098 .mu.m and Rmax
(Maximum height roughness) is 36.297 .mu.m to 39.059 .mu.m. The
convex portions on the outer peripheral surface of the fixing
roller 13 are removed away by polishing so that irregularities in
the fluorocarbon polymers or silicone rubber to be coated in the
later step become small. That is, the surface roughness in the
outer peripheral surface of the aluminum surface layer by Rmax
(Maximum height roughness) is preferable to be no more than 40
.mu.m, specifically preferable to be 10 .mu.m to 40 .mu.m.
[0056] Next, the outer peripheral surface of the aluminum surface
layer 401 of the fixing roller 13 having been polished is degreased
and cleaned in STEP 7 shown in FIG. 3. Primer coating is applied,
with a spraying gun, to the outer peripheral surface of the
aluminum surface layer 401 that has been degreased and cleaned in
STEP 8 shown in FIG. 3. Water-based paint containing
polytetrafluoroethylene resin as a main component was used for
primer. STEP 9 shown in FIG. 3 is the last step, in which the outer
peripheral surface to which primer coating has been applied is
coated with elastic material such as silicone rubber or
fluorocarbon polymers having releasing property by use of a
spraying gun to form a releasing layer (surface layer) 402. With
this step, the fixing roller 13 is accomplished, which affords
uniform fixing of toner 11 following the paper 12 and improvement
in releasing property.
[0057] (Thickness of Aluminum Surface Layer)
[0058] The outer peripheral surface of the tubular body of a
stainless steel material is covered with an aluminum surface layer
formed by thermal spraying. The thickness t2 of this aluminum
surface layer 401 is 20 .mu.m to 30 .mu.m in the above mentioned
embodiment. In the case where the thickness of the aluminum surface
layer is thin compared with the tubular body of a stainless steel
material, the effect of restraining temperature rise in the end
portions becomes less. The following table 1 shows a result
obtained by measuring temperature rise in the end portions with the
thickness of the aluminum surface layer fixed to be 30 .mu.m and
the thickness of the tubular body of a stainless steel material
being varied.
TABLE-US-00001 TABLE 1 Temperature at ends and thickness of base
layer in fixing roller SUS Al Ratio Temerature (.mu.m) (.mu.m) (%)
rise in ends Decision 150 30 20 low OK 200 30 15 low OK 250 30 12
high NG
[0059] From this result, it is clarified that the temperature in
the end portions becomes high when the ratio of the thickness of
the aluminum surface layer to that of the tubular body of a
stainless steel material is 12%. It is necessary for the thickness
of the aluminum surface layer to be 10 .mu.m or more, since cavity
occurs when the thickness is less than 10 .mu.m. The thickness of
aluminum surface layer is more preferable to be more than 20 .mu.m.
In general, the thickness of the tubular body of a stainless steel
material as a base layer of a fixing sleeve is 20 .mu.m to 50
.mu.m, considering mechanical strength and heat capacity. Similarly
considering, the thickness of the tubular body of a stainless steel
material as a base layer of a fixing roller is 100 .mu.m to 300
.mu.m in general. Consequently, considering the maximum thickness
of the base layer of the fixing roller as being about 300 .mu.m, it
may be sufficient for the thickness of the aluminum surface layer
to be more than 15% in ratio to that of the base layer of a
stainless steel material, as seen from Table 1. However, too much
thickness brings a waste of materials. Since the thickness of the
base layer of a stainless steel material of a fixing roller is
about 300 .mu.m at most, the maximum thickness of the aluminum
surface layer, being at most 50% of the base layer of a stainless
steel material, is restricted to 150 .mu.m.
[0060] From these, it is suitable that the thickness of the
aluminum surface layer of a fixing roller or a fixing sleeve is in
the level of 10 .mu.m to 150 .mu.m. Preferably, the thickness of
the aluminum surface layer is 20 .mu.m to 25 .mu.m for a fixing
sleeve and 10 .mu.m to 150 .mu.m for a fixing roller. To say this
thickness of the aluminum surface layer by the ratio to the
thickness of the stainless steel material as a base layer, it is
suitable for the aluminum surface layer to be 15% to 50% of the
thickness of the stainless steel material as a base layer.
[0061] In the fixing device according to the present invention
using a stainless steel material, a thin aluminum surface layer is
formed on the outer peripheral surface of a tubular body made of a
thin stainless steel material as a base layer, so that temperature
rising speed in the thickness direction is high, temperature
distribution is uniform in the axial direction with little thermal
unevenness on the fixing member and less energy is required for
heating the fixing member. Further, a halogen heater can be used as
a heating element, heating of the fixing member can be made just
after turning on of the power switch and stability of the device
can be provided along with less expense required, since the fixing
member has a small heat capacity. While examples where a halogen
lamp is used as a heating element has been explained for
embodiments, other heating elements such as a ceramic heater, an
electromagnetic induction coil, etc.
* * * * *